The present invention relates to a magnetic disk apparatus, and in particular to a magnetic disk apparatus disposed with a dual stage actuator.
In order to accommodate the increase in recording density accompanying the increase in the recording capacity of magnetic disk apparatus of recent years, there are magnetic disk apparatus configured to position the magnetic head at a predetermined position using a head positioning mechanism called a dual stage actuator. This type of head moving mechanism comprises a coarse actuator, whose movable range is large but whose positioning precision is low, and a fine actuator, whose movable range is small but whose positioning precision is high, and attempts to realize high positioning precision in a wide movable range by controlling these.
As this type of conventional magnetic disk apparatus, there is the magnetic disk apparatus described in JP-A-2001-6305 (Patent Document 1).
As shown in FIG. 7, this magnetic disk apparatus is schematically configured by a sampler 21, an A/D converter 22, a code inverter 23, a fine controller 24, a coarse controller 25, a limiter 26, a subtracter 27, a multiplier 28, D/A converters 29 and 30, and filters 31 and 32. The sampler 21 samples, at predetermined periods, a position error signal SE supplied from a microunit of a head moving mechanism 1, and supplies this to the A/D converter 22. The A/D converter 22 digitally converts the output signal of the sampler 21 into discrete position error data DE and supplies this to the coder inverter 23. The code inverter 23 inverts the code of the position error data DE and supplies this to the fine controller 24.
In this magnetic disk apparatus, a positioning controller is disclosed with correcting means having saturating means 26 that saturates a fine control signal DC1 to within a limit corresponding to the operating range of the fine actuator and supplies this to the fine actuator and which uses a multiplier 28 to multiply an appropriate gain with a difference signal between an output signal DL of the saturating means 26 and the fine control signal DC1 to generate a correction signal DA for correcting the fine control signal DC1.